Effects of rearing temperature on yolksac volume and growth rate in Lake Sturgeon, A. fulvescens, from hatch to age-1

Abstract

In fishes, differences in egg incubation and water temperature in early rearing environments can have a significant impact on phenotypic development. This is particularly relevant during the first year of life when growth rate peaks and influences an individual's life history trajectory. In the present study, we examined the effect of differences in egg incubation, water temperature and overwintering on growth in Lake Sturgeon, A. fulvescens, throughout the first year of life. Developing embryos were incubated at 12–14 °C supplied with flow-through water and ambient light conditions in MacDonald hatching jars or allowed to adhere to substrate. Upon hatch (~9 days post-fertilization, dpf) larvae from each incubation treatment were then transferred to 16, 18 or 20 °C water increasing at a rate of 0.5 °C.day−1 and held at those temperatures until approximately 24 days post-hatch (dph). Experimental treatments were then transferred to a common garden set-up where duplicate treatment tanks were fed flow through river water at ambient temperature with natural light cycles. These were compared to fish transferred from a standard hatchery rearing treatment to the common garden tanks at the same time. Experimental fish were fed ad libitum twice daily throughout the growing season, but food was withheld when water temperature reached 1.5 °C (~6 months post-hatch, mph). Food was re-introduced at the start of spring the following year when water temperature exceeded 2 °C for three days in a row, (~ 10.5 mph). In experimental treatments, growth rate was highest in the 20 °C group during the first 3 months but converged with all other experimental treatments during winter before once again exceeding the other treatments following recovery from overwintering. Our data suggest that a temperature dependent growth phenotype was fixed during the first month of life in Lake Sturgeon that could have significant implications on hatchery rearing of this endangered species for conservation purposes.